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Dr. David H. Ley

Dr. David H. Ley

Professor, Poultry Health Management
Diplomate, American College of Veterinary Microbiologists
Diplomate, American College of Poultry Veterinarians

Phone: 919.513.6269
Fax: 919.513.6464
Email: david_ley@ncsu.edu
Curriculum vitae (CV)

Education

  • BS - Biological Sciences, University of California, Irvine, 1971
  • MA - Microbiology, University of California, Davis, 1976
  • DVM - University of California, Davis, 1982
  • PhD - Microbiology, University of California, Davis, 1982

Areas of Research/Study

  • Poultry diseases
  • Avian mycoplasmosis
  • Biosecurity
  • Identification and control of emerging diseases
  • Enteric and respiratory disease pathogenesis
  • Interaction of management and disease

Mycoplasma species are important respiratory tract and systemic pathogens of commercial poultry causing substantial economic losses worldwide due to increased mortality, downgrading and condemnations of carcasses, reduced egg production and hatchability, and decreased feed efficiency. Strategies to reduce the adverse impact of mycoplasmosis in commercial poultry include

  1. surveillance, control, and eradication programs
  2. use of antimicrobials, and
  3. vaccination.

Research in my laboratory is focused on improving the health of commercial poultry by developing new knowledge that will contribute to the elimination or reduction of losses due to mycoplasmosis. Specific objectives are to 1) develop and evaluate rapid diagnostic capabilities for the identification of Mycoplasma species and strains causing diseases, 2) delineate the epidemiology of avian mycoplasmosis by developing and using strain-specific molecular markers, and 3) design and implement novel immune prophylactic strategies for effective control of avian mycoplasmosis.

Pathophysiological investigations have been aimed at identifying virulence factors, especially adhesins: immunodominant integral membrane proteins that attach the microbe to host cells. Genes encoding these proteins could be cloned, and the expressed proteins used as reagents in diagnostic tests, or as immunogens in subunit or vectored vaccines. Epidemiology of avian mycoplasmosis is being investigated using random amplification of polymorphic DNA (RAPD), which enables us to quickly and easily identify strains within a Mycoplasma sp. This method and newer approaches such as amplified fragment length polymorphism (AFLP) and/or targeted gene sequencing are very promising for disease outbreak investigations and for the ability to differentiate various vaccine strains from each other and field strains.

Mycoplasma gallisepticum (MG) conjunctivitis emerged in 1994 as a disease of free-ranging house finches (Carpodacus mexicanus) in the eastern United States and has since spread to house finches throughout their entire eastern range. The resulting epidemic of MG conjunctivitis produced an unprecedented decline of eastern house finch populations, and the endemic disease remains associated with repeating seasonal peaks of disease and limitation of host populations. MG has also been isolated from other songbirds with conjunctivitis including American goldfinches, a blue jay, purple finches, and evening and pine grosbeaks. RAPD fingerprinting demonstrated the presence of what appeared to be a single, unique RAPD profile among house finch and other songbird MG isolates, suggesting a single point source of origin and one 'strain' common to the outbreak. However, genomic variability of MG house finch isolates has recently been identified by PCR-RFLP and nucleotide sequencing of the pvpA gene. These findings suggested that house finch MG isolates may be more polymorphic than previously recognized and provide evidence of molecular evolution.

We have seen some evidence of genomic variability among MG isolates by RAPD fingerprinting. However, RAPD fingerprints are prone to variability, and may be difficult to reproduce and standardize, making interpretation challenging and subjective. More extensive analyses of historical and contemporary isolates of MG from house finches and other songbirds, using improved genotyping techniques such as AFLP or targeted gene sequencing could help resolve questions about the epidemiology and molecular evolution of MG conjunctivitis in house finches and other songbirds.

Appointments and Honors

  • Professor, Department of Population Health & Pathobiology, College of Veterinary Medicine, North Carolina State University; 1997-present.
  • Visiting Research Fellow, University of Melbourne (Australia), Department of Veterinary Science; 6/93-4/94.
  • Associate Professor, Department of Food Animal & Equine Medicine, College of Veterinary Medicine, North Carolina State University; 1989-1997.
  • Assistant Professor, Department of Food Animal & Equine Medicine, College of Veterinary Medicine, North Carolina State University; 1984-1989.
  • NCSU-CVM Class of 2004 Faculty Teaching Award; 2003.
  • NC State University Alumni Outstanding Research Award Nominee: 2000-2001.
  • Recipient of a congratulatory resolution from the National Poultry Improvement Plan; 2000.
  • Best Poster, AVMA/AAAP Annual Meeting; 1996.
  • Best Poster, AVMA/AAAP Annual Meeting; 1995.
  • Phi Zeta Honor Society of Veterinary Medicine: Member Elect; 1989
  • United States Department of Agriculture Animal Health Science Research Advisory Board Nominee; 1986.

Representative Publications

Scientific Papers

  • Ley DH, Berkhoff JE and JM McLaren. Mycoplasma gallisepticum isolated from house finches (Carpodacus mexicanus) with conjunctivitis. Avian Dis. 40:480-483. 1996.
  • Ley DH, JM McLaren, AM Miles, HJ Barnes, S Heins Miller and G Franz. Transmissibility of live Mycoplasma gallisepticum vaccine strains ts-11 and 6/85 from vaccinated layer pullets to sentinel poultry. Avian Dis. 41:186-193. 1997.
  • Noormohammadi AH, PF Markham, KG Whithear, ID Walker, VA Gurevich, DH Ley, and GF Browning. Mycoplasma synoviae has two distinct phase-variable major membrane antigens, one of which is a putative hemagglutinin. Infection and Immunity 65:2542-2547. 1997.
  • Ley DH, JE Berkhoff and S Levisohn. Molecular epidemiological investigations of Mycoplasma gallisepticum (MG) conjunctivitis in songbirds by random amplified polymorphic DNA (RAPD) analyses. Emerging Infectious Diseases, 3:375-380. 1997.
  • Ley DH, Geary SJ, Berkhoff JE, McLaren JM and Levisohn S. Mycoplasma sturni from blue jays and northern mockingbirds with conjunctivitis in Florida. Journal of Wildlife Diseases, 34:403-406. 1998.
  • Hartup BK, Kollias GV, Ley DH. Mycoplasmal conjunctivitis in songbirds from New York. Journal of Wildlife Diseases, 36:257-264. 2000.
  • Mikaelian I, Ley DH, Claveau R, Lemieux M, Berube J-P. Mycoplasmosis in evening and pine grosbeaks with conjunctivitis in Quebec. J Wildl Dis 37:826-830. 2001.
  • Hartup BK, Bickal JM, Dhondt AA, Ley DH, Kollias GV. Dynamics of conjunctivitis and Mycoplasma gallisepticum infections in house finches. The Auk 118(2):327-333. 2001.
  • Pakpinyo S, Ley DH, Barnes HJ, Vaillancourt JP, Guy JS. Prevalence of enteropathogenic Escherichia coli in naturally occurring cases of poult enteritis-mortality syndrome. Avian Diseases, 46:360-369. 2002.
  • Pakpinyo S, Ley DH, Barnes HJ, Vaillancourt JP, Guy JS. Enhancement of enteropathogenic Escherichia coli pathogenicity in young turkeys by concurrent turkey coronavirus infection. Avian Diseases, 47:396-405. 2003.
  • Pillai, SR, Mays HL, Jr., Ley DH, Luttrell P, Panangala VS, Farmer KL, Roberts SR. Molecular variability of house finch Mycoplasma gallisepticum isolates as revealed by sequencing and restriction fragment length polymorphism analysis of the pvpA gene. Avian Diseases, 47:640-648. 2003.
  • Kollias GV, Sydenstricker KV, Kollias HW, Ley DH, Hosseini PR, Connolly V, Dhondt AA. Experimental infection of house finches with Mycoplasma gallisepticum. Journal of Wildlife Diseases, 40:79-86. 2004.
  • Hartup BK, Stott-Messick B, Guzy M, Ley DH. Health survey of house finches (Carpodacus mexicanus) from Wisconsin. Avian Diseases, 48:84-90. 2004.
  • Hong Y, Garcia M, Levisohn S, Savelkoul P, Leiting V, Lysnyansky I, Ley DH, Kleven SH. Differentiation of Mycoplasma gallisepticum strains using amplified fragment length polymorphism and other DNA-based typing methods. Avian Diseases 49:43-49. 2005.
  • Dhondt AA, Altizer S, Cooch EG, Davis AK, Dobson A, Driscoll MJL, Hartup BK, Hawley DM, Hochachka WM, Hosseini PR, Jennelle CS, Kollias GV, Ley DH, Swarthout ECH, Sydenstricker KV. Dynamics of a novel pathogen in an avian host: Mycoplasmal conjunctivitis in house finches. Acta Tropica Vol. 94, No. 1, pp 77-93. 2005.
  • Sydenstricker KV, Dhondt AA, Ley DH, Kollias GV. Re-exposure of captive house finches that recovered from Mycoplasma gallisepticum infection. Journal of Wildlife Diseases 41:326-333. 2005.
  • Cherry JJ, Ley DH, Altizer S. Genotypic analyses of Mycoplasma gallisepticum isolates from songbirds by random amplification of polymorphic DNA and amplified-fragment length polymorphism. Journal of Wildlife Diseases. In press 2005.

Books

  • Ley DH, HW Yoder, Jr. Mycoplasma gallisepticum infection. In: Diseases of Poultry, 10th ed, BW Calnek, HJ Barnes, CW Beard, LR McDougald, YM Saif, eds. Ames, Iowa: Iowa State University Press, pp. 194-207. 1997.
  • Ley DH. Mycoplasma gallisepticum infection. In: Diseases of Poultry, 11th ed, BW Calnek, HJ Barnes, CW Beard, LR McDougald, YM Saif, eds. Ames, Iowa: Iowa State University Press, pp. 722-744. 2003.

NC State College of Veterinary Medicine 4700 Hillsborough Street, Raleigh, NC 27606(919) 513-6786